{ "document": { "category": "csaf_base", "csaf_version": "2.0", "distribution": { "tlp": { "label": "WHITE" } }, "lang": "en", "notes": [ { "category": "legal_disclaimer", "text": "The Netherlands Cyber Security Center (henceforth: NCSC-NL) maintains this portal to enhance access to its information and vulnerabilities. The use of this information is subject to the following terms and conditions:\n\nThe vulnerabilities disclosed in this portal are gathered by NCSC-NL from a variety of open sources, which the user can retrieve from other platforms. NCSC-NL makes every reasonable effort to ensure that the content of this portal is kept up to date, and that it is accurate and complete. Nevertheless, NCSC-NL cannot entirely rule out the possibility of errors, and therefore cannot give any warranty in respect of its completeness, accuracy or real-time keeping up-to-date. NCSC-NL does not control nor guarantee the accuracy, relevance, timeliness or completeness of information obtained from these external sources. The vulnerabilities disclosed in this portal are intended solely for the convenience of professional parties to take appropriate measures to manage the risks posed to the cybersecurity. No rights can be derived from the information provided therein.\n\nNCSC-NL and the Kingdom of the Netherlands assume no legal liability or responsibility for any damage resulting from either the use or inability of use of the vulnerabilities disclosed in this portal. This includes damage resulting from the inaccuracy of incompleteness of the information contained in it.\nThe information on this page is subject to Dutch law. All disputes related to or arising from the use of this portal regarding the disclosure of vulnerabilities will be submitted to the competent court in The Hague. This choice of means also applies to the court in summary proceedings." } ], "publisher": { "category": "coordinator", "contact_details": "cert@ncsc.nl", "name": "National Cyber Security Centre", "namespace": "https://www.ncsc.nl/" }, "title": "CVE-2026-25891", "tracking": { "current_release_date": "2026-03-26T18:51:29.053177Z", "generator": { "date": "2026-02-17T15:00:00Z", "engine": { "name": "V.E.L.M.A", "version": "1.7" } }, "id": "CVE-2026-25891", "initial_release_date": "2026-02-24T21:38:34.611230Z", "revision_history": [ { "date": "2026-02-24T21:38:34.611230Z", "number": "1", "summary": "CVE created.| Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| Products created (1).| References created (3).| CWES updated (1)." }, { "date": "2026-02-24T21:38:42.330153Z", "number": "2", "summary": "NCSC Score created." }, { "date": "2026-02-24T21:39:49.089074Z", "number": "3", "summary": "Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| References created (4).| CWES updated (1)." }, { "date": "2026-02-24T21:39:54.982400Z", "number": "4", "summary": "NCSC Score updated." }, { "date": "2026-02-24T22:32:18.346800Z", "number": "5", "summary": "Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| References created (3).| CWES updated (1)." }, { "date": "2026-02-24T22:32:26.723801Z", "number": "6", "summary": "NCSC Score updated." }, { "date": "2026-02-24T22:38:57.576018Z", "number": "7", "summary": "Unknown change." }, { "date": "2026-02-25T00:12:43.895096Z", "number": "8", "summary": "Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| Products connected (1).| References created (3).| CWES updated (1)." }, { "date": "2026-02-25T11:02:50.602304Z", "number": "9", "summary": "Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| Products connected (1).| References created (5).| CWES updated (1)." }, { "date": "2026-02-25T15:14:30.935449Z", "number": "10", "summary": "Source created.| CVE status created. (valid)| EPSS created." }, { "date": "2026-02-25T15:14:37.708880Z", "number": "11", "summary": "NCSC Score updated." }, { "date": "2026-02-27T00:12:57.406608Z", "number": "12", "summary": "Source created.| CVE status created. (valid)| Description created for source.| References created (3)." }, { "date": "2026-02-27T00:12:59.328456Z", "number": "13", "summary": "NCSC Score updated." }, { "date": "2026-02-27T03:24:59.744320Z", "number": "14", "summary": "CVSS created.| Products connected (1).| Product Identifiers created (1).| Exploits created (2)." }, { "date": "2026-02-27T03:25:02.033718Z", "number": "15", "summary": "NCSC Score updated." }, { "date": "2026-02-27T20:39:33.753346Z", "number": "16", "summary": "Description removed for source.| Description created for source.| References created (2)." }, { "date": "2026-02-27T20:39:42.068412Z", "number": "17", "summary": "NCSC Score updated." }, { "date": "2026-02-28T06:12:58.819731Z", "number": "18", "summary": "Description removed for source.| Description created for source.| References created (2)." }, { "date": "2026-03-20T09:45:50.992414Z", "number": "19", "summary": "Source connected.| CVE status created. (valid)| EPSS created." }, { "date": "2026-03-20T09:45:53.753759Z", "number": "20", "summary": "NCSC Score updated." }, { "date": "2026-03-26T18:48:03.602882Z", "number": "21", "summary": "Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| Products connected (2).| References created (7).| CWES updated (1)." }, { "date": "2026-03-26T18:48:05.824793Z", "number": "22", "summary": "NCSC Score updated." } ], "status": "interim", "version": "22" } }, "product_tree": { "branches": [ { "branches": [ { "branches": [ { "category": "product_version_range", "name": "vers:unknown/>=0|<3.1.0", "product": { "name": "vers:unknown/>=0|<3.1.0", "product_id": "CSAFPID-5700113" } }, { "category": "product_version_range", "name": "vers:unknown/>=3.0.0|<3.1.0", "product": { "name": "vers:unknown/>=3.0.0|<3.1.0", "product_id": "CSAFPID-5699780", "product_identification_helper": { "cpe": "cpe:2.3:a:gofiber:fiber:*:*:*:*:*:go:*:*" } } }, { "category": "product_version_range", "name": "vers:unknown/v3.0.0", "product": { "name": "vers:unknown/v3.0.0", "product_id": "CSAFPID-5702052" } } ], "category": "product_name", "name": "Fiber" } ], "category": "vendor", "name": "Gofiber" }, { "branches": [ { "branches": [ { "category": "product_version_range", "name": "vers:unknown/3.1.0", "product": { "name": "vers:unknown/3.1.0", "product_id": "CSAFPID-5918986" } }, { "category": "product_version_range", "name": "vers:unknown/<3.1.0", "product": { "name": "vers:unknown/<3.1.0", "product_id": "CSAFPID-5918987" } } ], "category": "product_name", "name": "go/github.com/gofiber/fiber/v3" } ], "category": "vendor", "name": "fiber" } ] }, "vulnerabilities": [ { "cve": "CVE-2026-25891", "cwe": { "id": "CWE-22", "name": "Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')" }, "notes": [ { "category": "description", "text": "Fiber is an Express inspired web framework written in Go. A Path Traversal (CWE-22) vulnerability in Fiber allows a remote attacker to bypass the static middleware sanitizer and read arbitrary files on the server file system on Windows. This affects Fiber v3 through version 3.0.0. This has been patched in Fiber v3 version 3.1.0.", "title": "cveprojectv5 - https://www.cve.org/CVERecord?id=CVE-2026-25891" }, { "category": "description", "text": "Fiber is an Express inspired web framework written in Go. A Path Traversal (CWE-22) vulnerability in Fiber allows a remote attacker to bypass the static middleware sanitizer and read arbitrary files on the server file system on Windows. This affects Fiber v3 through version 3.0.0. This has been patched in Fiber v3 version 3.1.0.", "title": "nvd - https://nvd.nist.gov/vuln/detail/CVE-2026-25891" }, { "category": "description", "text": "Fiber is an Express inspired web framework written in Go. A Path Traversal (CWE-22) vulnerability in Fiber allows a remote attacker to bypass the static middleware sanitizer and read arbitrary files on the server file system on Windows. This affects Fiber v3 through version 3.0.0. This has been patched in Fiber v3 version 3.1.0.", "title": "osv - https://www.googleapis.com/download/storage/v1/b/osv-vulnerabilities/o/GIT%2FCVE-2026-25891.json?alt=media" }, { "category": "description", "text": "Fiber has an Arbitrary File Read in Static Middleware on Windows in github.com/gofiber/fiber/v3", "title": "osv - https://www.googleapis.com/download/storage/v1/b/osv-vulnerabilities/o/Go%2FGO-2026-4540.json?alt=media" }, { "category": "description", "text": "### Summary\n\n**Description**\nA Path Traversal (CWE-22) vulnerability in Fiber allows a remote attacker to bypass the static middleware sanitizer and read arbitrary files on the server file system on Windows. This affects Fiber v3 through version 3.0.0. This has been patched in Fiber v3 version 3.1.0.\n \n### Details\nThe vulnerability resides in `middleware/static/static.go` within the `sanitizePath` function. This function attempts to sanitize the requested path by checking for backslashes, decoding the URL, and then cleaning the path.\n\nThe vulnerability stems from two combined issues:\n- The check for backslash characters happens before the URL decoding loop. If an attacker sends a double-encoded backslash, the initial check sees `%255C` and passes. The loop then decodes this into a single backslash.\n- The function uses `path.Clean` to clean the resulting string. `path.Clean` is designed for slash-separated paths and does not recognize backslashes as directory separators. Consequently, sequences like `..\\..\\` are treated as valid filenames.\n\nWhen this sanitized path is later used, the backslashes are interpreted as valid separators, allowing the attacker to traverse up the directory tree.\n```go\n// pkg/static/static.go\nfunc sanitizePath(p []byte, filesystem fs.FS) ([]byte, error) {\n ...\n // this check happens BEFORE decoding\n if bytes.IndexByte(p, '\\\\') >= 0 {\n ...\n } \n // This loop decodes %255C to %5C to \\\n for strings.IndexByte(s, '%') >= 0 {\n us, err := url.PathUnescape(s)\n ...\n s = us\n }\n // path.Clean only understands forward slashes (/)\n s = pathpkg.Clean(\"/\" + s)\n ...\n return utils.UnsafeBytes(s), nil\n}\n```\n\n### Impact\n\nThis impacts Fiber v3 prereleases through stable release version 3.0.0.\n\nSuccessful exploitation requires the server to be using the static middleware on Windows, as this is the only OS where backslashes are treated as directory separators by the file system.\n\nExploitation allows directory traversal on the host server. An attacker can read arbitrary files within the scope of the application server context. Depending on permissions and deployment conditions, attackers may access sensitive files outside the web root, such as configuration files, source code, or system files. Leaking application secrets often leads to further compromise.\n\n### Patches\n\nThis has been [patched](https://github.com/gofiber/fiber/pull/4064) in Fiber v3 version 3.1.0. Users are strongly encouraged to update to the latest available release.", "title": "github - https://github.com/advisories/GHSA-m3c2-496v-cw3v" }, { "category": "description", "text": "### Summary\n\n**Description**\nA Path Traversal (CWE-22) vulnerability in Fiber allows a remote attacker to bypass the static middleware sanitizer and read arbitrary files on the server file system on Windows. This affects Fiber v3 through version 3.0.0. This has been patched in Fiber v3 version 3.1.0.\n \n### Details\nThe vulnerability resides in `middleware/static/static.go` within the `sanitizePath` function. This function attempts to sanitize the requested path by checking for backslashes, decoding the URL, and then cleaning the path.\n\nThe vulnerability stems from two combined issues:\n- The check for backslash characters happens before the URL decoding loop. If an attacker sends a double-encoded backslash, the initial check sees `%255C` and passes. The loop then decodes this into a single backslash.\n- The function uses `path.Clean` to clean the resulting string. `path.Clean` is designed for slash-separated paths and does not recognize backslashes as directory separators. Consequently, sequences like `..\\..\\` are treated as valid filenames.\n\nWhen this sanitized path is later used, the backslashes are interpreted as valid separators, allowing the attacker to traverse up the directory tree.\n```go\n// pkg/static/static.go\nfunc sanitizePath(p []byte, filesystem fs.FS) ([]byte, error) {\n ...\n // this check happens BEFORE decoding\n if bytes.IndexByte(p, '\\\\') >= 0 {\n ...\n } \n // This loop decodes %255C to %5C to \\\n for strings.IndexByte(s, '%') >= 0 {\n us, err := url.PathUnescape(s)\n ...\n s = us\n }\n // path.Clean only understands forward slashes (/)\n s = pathpkg.Clean(\"/\" + s)\n ...\n return utils.UnsafeBytes(s), nil\n}\n```\n\n### Impact\n\nThis impacts Fiber v3 prereleases through stable release version 3.0.0.\n\nSuccessful exploitation requires the server to be using the static middleware on Windows, as this is the only OS where backslashes are treated as directory separators by the file system.\n\nExploitation allows directory traversal on the host server. An attacker can read arbitrary files within the scope of the application server context. Depending on permissions and deployment conditions, attackers may access sensitive files outside the web root, such as configuration files, source code, or system files. Leaking application secrets often leads to further compromise.\n\n### Patches\n\nThis has been [patched](https://github.com/gofiber/fiber/pull/4064) in Fiber v3 version 3.1.0. Users are strongly encouraged to update to the latest available release.", "title": "osv - https://www.googleapis.com/download/storage/v1/b/osv-vulnerabilities/o/Go%2FGHSA-m3c2-496v-cw3v.json?alt=media" }, { "category": "description", "text": "**Description**\nA Path Traversal (CWE-22) vulnerability in Fiber allows a remote attacker to bypass the static middleware sanitizer and read arbitrary files on the server file system on Windows. This affects Fiber v3 through version 3.0.0. This has been patched in Fiber v3 version 3.1.0.", "title": "gitlab - https://gitlab.com/api/v4/projects/25847700/repository/files/go%2Fgithub.com%2Fgofiber%2Ffiber%2Fv3%2FCVE-2026-25891.yml/raw" }, { "category": "other", "text": "0.00023", "title": "EPSS" }, { "category": "other", "text": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N", "title": "CVSSV4" }, { "category": "other", "text": "8.7", "title": "CVSSV4 base score" }, { "category": "other", "text": "3.4", "title": "NCSC Score" }, { "category": "other", "text": "Is related to (a version of) an uncommon product, The value of the most recent EPSS score, There is exploit data available from source Nvd", "title": "NCSC Score top decreasing factors" } ], "product_status": { "fixed": [ "CSAFPID-5918986" ], "known_affected": [ "CSAFPID-5699780", "CSAFPID-5700113", "CSAFPID-5702052", "CSAFPID-5918987" ] }, "references": [ { "category": "external", "summary": "Source - cveprojectv5", "url": "https://www.cve.org/CVERecord?id=CVE-2026-25891" }, { "category": "external", "summary": "Source raw - cveprojectv5", "url": "https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/25xxx/CVE-2026-25891.json" }, { "category": "external", "summary": "Source - github", "url": "https://github.com/advisories/GHSA-m3c2-496v-cw3v" }, { "category": "external", "summary": "Source raw - github", "url": "https://api.github.com/advisories/GHSA-m3c2-496v-cw3v" }, { "category": "external", "summary": "Source - nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-25891" }, { "category": "external", "summary": "Source raw - nvd", "url": "https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2026-25891" }, { "category": "external", "summary": "Source - osv", "url": "https://www.googleapis.com/download/storage/v1/b/osv-vulnerabilities/o/Go%2FGHSA-m3c2-496v-cw3v.json?alt=media" }, { "category": "external", "summary": "Source - osv", "url": "https://www.googleapis.com/download/storage/v1/b/osv-vulnerabilities/o/GIT%2FCVE-2026-25891.json?alt=media" }, { "category": "external", "summary": "Source - first", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-25891" }, { "category": "external", "summary": "Source raw - first", "url": "https://api.first.org/data/v1/epss?limit=10000&offset=0" }, { "category": "external", "summary": "Source - osv", "url": "https://www.googleapis.com/download/storage/v1/b/osv-vulnerabilities/o/Go%2FGO-2026-4540.json?alt=media" }, { "category": "external", "summary": "Source - first", "url": "https://api.first.org/data/v1/epss?limit=10000&offset=0" }, { "category": "external", "summary": "Source - gitlab", "url": "https://gitlab.com/api/v4/projects/25847700/repository/files/go%2Fgithub.com%2Fgofiber%2Ffiber%2Fv3%2FCVE-2026-25891.yml/raw" }, { "category": "external", "summary": "Reference - cveprojectv5; github; gitlab; nvd; osv", "url": "https://github.com/gofiber/fiber/security/advisories/GHSA-m3c2-496v-cw3v" }, { "category": "external", "summary": "Reference - cveprojectv5; github; gitlab; nvd; osv", "url": "https://github.com/gofiber/fiber/pull/4064" }, { "category": "external", "summary": "Reference - cveprojectv5; github; gitlab; nvd; osv", "url": "https://github.com/gofiber/fiber/commit/59133702301c2ab7b776dd123b474cbd995f2c86" }, { "category": "external", "summary": "Reference - github; gitlab", "url": "https://github.com/advisories/GHSA-m3c2-496v-cw3v" }, { "category": "external", "summary": "Reference - osv", "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/25xxx/CVE-2026-25891.json" }, { "category": "external", "summary": "Reference - github; gitlab; osv", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-25891" }, { "category": "external", "summary": "Reference - github; gitlab; osv", "url": "https://pkg.go.dev/vuln/GO-2026-4540" }, { "category": "external", "summary": "Reference - gitlab", "url": "https://github.com/gofiber/fiber" } ], "scores": [ { "cvss_v3": { "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N", "baseScore": 7.5, "baseSeverity": "HIGH" }, "products": [ "CSAFPID-5699780", "CSAFPID-5700113", "CSAFPID-5702052", "CSAFPID-5918987" ] } ], "title": "CVE-2026-25891" } ] }